The chief executive of Danske, Denmark’s largest bank, resigned Wednesday after a year-long internal investigation into money laundering found $233 billion in suspicious transactions moving through the bank’s tiny branch in Estonia — nearly 10 times larger than that country’s gross domestic product.

Danske said that CEO Thomas F. Borgen will continue in his position until his successor is named.

The scandal has rocked Denmark as suspicions grew that Danske had become a hub for Russian money laundering. The eye-popping figure, which was released in a report Wednesday by a law firm hired by the bank’s board, could make the case for one of the biggest money-laundering cases in history.

That report, by the firm Bruun & Hjejle, said the bank ignored years of signals about problematic transactions at its Estonia branch, including a warning in 2007 about “criminal activity in its pure form” involving “billions of rubles monthly.”

The bank is likely to face huge fines and investigations around the globe, including a criminal probe in Denmark and other legal action by European and U.S. investigators. The bank has lost about 30 percent of its market value this year, including a 3 percent drop Wednesday, as it scrambles to contain the growing crisis.

Denmark is also threatening to draft tougher penalties against money laundering.

“It is important to get one of the toughest levels of fines in Europe to signal we’re taking this very seriously, because this case has damaged Denmark’s image a lot,” Lisbeth Bech Poulsen, a spokeswoman for the opposition Socialist People’s Party, told Reuters. Financial penalties should be increased by up to 700 percent, Poulsen said.

The report said that the investigation still does not know much will ultimately be deemed illicit of the $233 billion that has been identified. So far, Danske has investigated 6,200 high-risk customer accounts but has many thousands more to go, according to the report. Almost all of those customers have been reported to authorities. “Overall, we expect a significant part of the payments to be suspicious,” the bank said.

Still, the sheer volume of the transactions should have raised alarms, said Nienke Palstra, an anti-money laundering campaigner for Global Witness, a London-based nonprofit organization. “There is no way that senior management would not have noticed that,” she said.

“There is no doubt that the problems related to the Estonian branch were much bigger than anticipated,” Ole Andersen, chairman of Danske’s board, said in a statement. “The findings of the investigations point to some very unacceptable and unpleasant matters at our Estonian branch.”

Danske’s branch in Estonia, a Baltic former Soviet Republic, operated independently from the rest of the bank with its own information technology system and many documents written in Estonian or Russian, according to the 87-page report. But there were “serious” indications of problems that the Danske never acted on. The branch, for example, had a lot of nonresident customers who “carried out large volumes of transactions that should have never happened,” according to the report. The bank said it suspects that some employees helped or collaborated with the customers.

In 2007, the Russian Central Bank warned that it was concerned some of its customers were connected to money laundering or other potential crimes estimated at “billions of rubles monthly,” according to the report. About 177 customers could be involved in what is known as the “Russian Laundromat,” an alleged money laundering scheme, and the investigation is also reviewing allegations of $230 million tax fraud involving “high-ranking officials in the Russian Government,” the report says. In 2013, a whistleblower, an employee at the Estonia branch, reported that “the bank knowingly continued to deal with a company that had committed a crime,” according to the report.

The bank did not launch its internal investigation until 2017.

Danske said it has since improved its anti-money laundering operations and would donate about $230 million in profit to a foundation to combat financial crime.

Borgen, the chief executive, said in a statement that ”it is clear that Danske Bank has failed to live up to its responsibility.”

“I deeply regret this,” Borgen added. “It has been clear to me for some time that resigning would be the right thing to do, but I have held off the decision, because I have felt a responsibility for seeing the bank through this difficult period toward presentation of the investigations.”